The composition and stability of vaginal microbiota have critical implications for the health of women and children. Disruptions in the composition of the vaginal microbiota leading to increased pH and decreased Lactobacilli abundance and diversity, called dysbiosis, occur in over 29% of reproductive-aged women and are associated with severe reproductive tract sequelae including postpartum infection, adverse outcomes in future pregnancies and increased susceptibility to sexually transmitted infections. Moreover, neonates begin to form the basis of their own microbiome during birth and suboptimal colonization can lead to short and long-term health problems, such as respiratory distress at birth and childhood asthma and allergies. Factors leading to dysbiosis include the use of vaginal lubricants. Components in lubricants have the potential to alter the composition of vaginal microbiota. The relationship between dysbiosis and vaginal lubricants is concerning because lubricants are often used by healthcare practitioners to perform intrapartum vaginal exams. Previous studies and feasibility testing for this proposal show that women receive many exams during labor, suggesting that lubricant exposure occurs frequently during the labor process. However, no studies have examined the vaginal microbiota during labor. This study aims to characterize the composition and changes in the vaginal microbiota during labor, with a focus on effects from lubricants used during vaginal exams. A cohort of 50 low-risk primigravid women will be recruited and followed for approximately 12 weeks. Mid-vaginal swabs and vaginal pH samples will be collected before labor (36 weeks gestation), at 2 points during labor and at 6-8 weeks postpartum. Molecular-based techniques will be used to identify the dominant species of microbes at each time point. A chart review will allow for the collection of clinical birth data, including number of vaginal exams performed during labor. Multiple linear regression and linear mixed models will be used to analyze changes in proportions of dominant microbial species over time, particularly as related to the number of vaginal exams received during labor. Other potential predictors include ethnicity, age, medication use, smoking status and clinical labor factors. Findings have the potential to translate into safer obstetrical practices and improved maternal and child health.